Photobiomolecular metallic particles and films

ABSTRACT

The method of the invention is based on the unique electron-carrying function of a photocatalytic unit such as the photosynthesis system I (PSI) reaction center of the protein-chlorophyll complex isolated from chloroplasts. The method employs a photo-biomolecular metal deposition technique for precisely controlled nucleation and growth of metallic clusters/particles, e.g., platinum, palladium, and their alloys, etc., as well as for thin-film formation above the surface of a solid substrate. The photochemically mediated technique offers numerous advantages over traditional deposition methods including quantitative atom deposition control, high energy efficiency, and mild operating condition requirements.

This is a divisional of application Ser. No. 09/310,414, now U.S. Pat.No. 6,162,278 filed May 12, 1999.

The U.S. Government has a paid-up license in this invention and theright in limited circumstances to require the patent owner to licenseothers on reasonable terms as provided for by the terms of Grant No.S-90,842 awarded by the Department of Energy.

BACKGROUND OF THE INVENTION

This invention relates generally to metallic particles and films, andmore particularly to methods for their production by linking theelectron pumping features of certain biological systems, such as thephotosynthetic machinery, with the reductive precipitation of metallicparticles.

Photosynthesis is the biological process that converts electromagneticenergy into chemical energy through light and dark reactions. In greenalgae and higher plants, photosynthesis occurs in specializedorganelles, called chloroplasts. The chloroplast is enclosed by a doublemembrane and contains thylakoids, consisting of stacked membrane disks(called grana) and unstacked membrane disks (called stroma). Thethylakoid membrane contains two key photosynthetic components,photosystem I and photosystem II, designated PSI and PSII, respectively,as depicted schematically in FIG. 1. During photosynthesis, water issplit into molecular oxygen, protons and electrons by PSII. Electronsderived from the splitting of water molecules are transported through aseries of carriers to PSI where they are further energized by alight-induced photochemical charge separation and transported across thethylakoid membrane where they are used for the enzymatic reduction ofNADP⁺ to NADPH. This biological reaction is further utilized forchemical energy production, primarily in the form of ATP.

Ultrafine metallic particles, e.g., nanoparticles, are importantprecursors for use in the fabrication of advanced material structures,such as thin continuous films. Conventionally, metallic films have beendeposited on substrates by methods such as chemical vapor deposition(CVD), sputtering, plating, and the like. Unfortunately, such methods donot generaly offer a degree of control desired for the deposition ofnanostructured materials, e.g., films having nanometer range thicknessesor grains. Therefore, a method which could drive the nucleation, growthand deposition of nanoparticles in a quantitative, rapid, andenergy-efficient manner would be highly desirable for many applications,including materials processing, catalysis, separations, electronics,energy production processes, and environmental applications.

Despite the extensive investigation concerning the photosyntheticmachinery, the use of photosynthesis-related principles for materialssynthesis and processing has not been described. The present invention,by exploiting the electron pumping characteristics of the photosyntheticmachinery for nanoparticle production and processing applications,provides improved methods and materials which overcome or at leastreduce the effects of one or more of the aforementioned problems.

SUMMARY OF THE INVENTION

This invention broadly concerns methods for the controlled deposition ofultrafine metallic particles and thin films via biomolecular electronicmechanisms. In particular, the invention takes advantage of theelectron-pumping characteristics of photosynthesis system I (PSI), andother biological systems having similar features, for photocatalyticallyreducing metal precursor chemicals into metallic nanostructuredmaterials.

Therefore, according to one aspect of the invention, a metallic film isformed by providing a liquid suspension which is at least partlycomprised of a plurality of photosystem I-containing units, metalprecursors, and any other component necessary or desired for effectingthe photochemical reaction on the PSI-containing unit, e.g., electrondonor molecules. The liquid suspension is contacted with light,preferably in the form of intermittent flashes, under conditionseffective for causing the controlled reductive precipitation of themetal precursors on the photosystem I-containing units to formphotosystem I-metal complexes. Generally, the liquid suspensioncontaining the photosystem I-metal complexes is provided above thesurface of a solid or semisolid substrate, such as a surface comprisedof gold, silicon, silica, alumina, zirconia, titania, or any of avariety of other materials. Thereafter, the liquid of the liquidsuspension is removed, for example by applying heat and/or vacuum toevaporate the liquid. Upon removal of the liquid, a film is therebyformed on the surface of the substrate that is at least partly comprisedof the metal from the photosystem I-metal complexes.

In another aspect of the invention, a plurality of PSI-containing unitsmay be anchored or otherwise coated on a desired substrate prior toperforming the photo-induced formation of the photosystem I-metalcomplexes. This PSI-coated substrate is then contacted with a solutioncontaining a plurality of metal precursors, electron donor molecules andother desired components. The solution and the underlying PSI-coatedsubstrate are thereafter contacted with light energy under conditionseffective for causing the reductive precipitation of the metal precusoron the photosystem I-containing unit to form photosystem I-metalcomplexes that are spatially constrained along the surface of thesubstrate. Under appropriate reaction conditions, the metal particles onthe PSI-containing units are controllably grown to a size at which metalparticles on adjacent PSI-containing units above the substrate mergeinto a continuous metallic film.

In another aspect of the invention, metallic nanoparticles are providedby forming PSI-metal complexes in a suitable liquid suspension andthereafter separating the metal particles from the PSI-metal complexes.The means by which the metal particles are separated may include anysuitable chemical, physical or mechanical treatment sufficient to removethe particles from the complexes without adversely affecting theirchemical composition or structural integrity.

The methods of the present invention offer numerous advantages overother technologies, e.g., CVD, sputtering, electroless plating, MBE,etc., for the production of metallic particles, films, and othermaterials such as alloys and composites. First the methods allow forprecisely controlled metal particle nucleation and growth foratomic-level deposition. The methods are energy-efficient and have norequirement for high temperature or pressure/vacuum systems, such as arerequired for other technologies. Moreover, the methods offercontrollable deposition kinetics which may be varied through modulationof the light energy input level. Finally, the methods areenvironmentally benign and non-interfering, i.e, light is thecontrolling mechanism.

The nanosized particles of this invention, and the products derivedtherefrom, will support a broad range of applications, includingenergetics (e.g., as fuel in propellants), explosives, microelectronics,catalysis, powder metallurgy, coating and joining technologies, andothers. For example, for catalysis/separations applications, reductionsin metallic film thicknesses will reduce metal cost, allow higherhydrogen flux, enhance permselectivity, and improve membrane reactorefficiency. The membrane reactors have been used in energy generationand environmental application processes, such as the advanced powergeneration and environmental application processes, such as the advancedpower generation systems-integrated gasification combined cycle (IGCC)systems.

In the petrochemical industry, important applications may includehydrogen separation and membrane reactions concerning hydrocarbon (suchas propane and ethylbenzene) dehydrogenation and natural gas steamreforming (e.g., CH₄+H_(z)O→CO+3H₂), oxidative reforming of methane tosyngas, and partial oxidation or oxidative coupling of methane intohydrogen and higher hydrocarbons. For these chemical reactions,palladium (Pd)-based membranes may be preferred in terms of temperatureresistance and hydrogen permeability, however other metals, e.g.,platinum and osmium, may also be used. In addition, metallicnanoparticle arrays of uniform particle size in the range of about2.5-100 nm deposited over a large area oxide (1 cm²) support offerpromising alternatives to single crystal surface catalysts.

The methods of the invention also find use in a variety of applicationsinvolving electronic materials and devices, such as electronic circuitboard fabrication, metallic (Pd) buffer layer preparation forsuperconducting RABiTS (Rolling-Assisted Biaxially Textured Substrate),and multilayer devices (such as hard disk reading head memory chip)based on GMR (Giant Magnetorresistance).

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be best understood by reference to the followingdescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 depicts schematically a simplified representation oflight-induced electron transport through the photosynthetic machinery ofthe thylakoid membrane;

FIG. 2 illustrates the production of a light-induced PSI-metal complexin a liquid suspension which contains metal precursors, electron donorsand PSI-containing units. The metal precursors in the suspension undergoreductive precipitation at the reducing end of PSI to form a metalparticles, the sizes of which may be controlled by the amount of lightprovided; and

FIG. 3 illustrates one embodiment of the invention whereinPSI-containing units are coated/anchored on a suitable substrate. ThePSI-coated substrate is contacted with a solution containing metalprecursors and electron donor molecules, and light energy is appliedunder condition for forming the desired PSI-metal complexes. As themetal particles of the PSI-metal complexes grow larger in response to acontinued application of light energy, the particles can merge bybiomolecular “welding” to form a continuous metal film over thesubstrate.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spiritand scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions must be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

According to the present invention, metallic nanoparticles and films areproduced by light-mediated reactions between the reducing end of aPSI-containing unit and metal precursor compounds. The reactions aregenerally carried out in a liquid suspension containing metal precursorcompounds and electron donor molecules such that thephotoelectrodeposition and nanoparticle growth is induced on thereducing end of PSI reaction centers by the controlled administration oflight energy. For example, by using a pulsed light source, metalprecipitation on the reducing end of PSI, and consequently the size ofmetal particles generated, can be controlled at the atomic level, e.g.by precise deposition of one metal atom at a time.

Metallic nanoparticles, or metallic particles, as the terms are usedherein, refer to the those particles attainable by the methods of theinvention. The size of the nanoparticles so produced are not strictlylimited, and may range, for example, from less than 1 nm to greater than1000 nm or more. However, certain advantages may be realized when thenanoparticles have diameters in the range of about 1 nm to 100 nm.Preferably, the nanoparticles will have diameters in the range of about1 nm to 10 nm. The metallic nanoparticles may be separated from thePSI-containing units after they are produced or may be used while stillcoupled to the PSI-containing units, depending on the particularapplication.

The PSI-containing units used in accordance with the present inventionwill preferably be comprised of isolated thylakoids or PSI particlesprepared, for example, from spinach chloroplasts. Methods for theisolation and preparation of thylakoids and PSI particles are well knownin the art (see, for example, Boardman, 1971; Setif et al., 1980; Reevesand Hall, 1980). Of course other PSI-containing units or photoelectronpumping units may also be used. For example, the PSI-containing unit maybe comprised of any of a variety of combinations of photosyntheticand/or other cellular or non-cellular components provided thePSI-containing unit contains the components necessary for effectingreductive precipitation of the desired metal precursor. ThePSI-containing unit, as the phrase is used in the context of thisinvention, may include other electron pumping cellular machineries fromplant or non-plant organisms. The skilled individual will appreciatethat other biological photochromic units (such as PSII, bacteriallight-sensitive proteins, bacteriorhodopsin, photocatalyticmicroorganisms, and algae) or a biotic photocatalytic unit such as TiO₂and pigments (e.g., proflavine and rhodopsin), may be suitable sincethese systems also possess a mechanism for light-induced electronpumping. Moreover, one could also produce electron pumping systems usingself-assembled-monolayers containing light sensitive organic dyes.

PSI is a protein-chlorophyll complex that is part of the photosyntheticmachinery within the thylakoid membrane (see FIG. 1). It is ellipsoidalin shape and has dimensions of about 5 by 6 nanometers. The photosystemI reaction center/core antenna complex contains about 40 chlorophyllsper photoactive reaction center pigment (P700). The chlorophyllmolecules serve as antennae which absorb photons and transfer the photonenergy to P700, where this energy is captured and utilized to drivephotochemical reactions. In addition to the P700 and the antennachlorophylls, the PSI complex contains a number of electron acceptors.An electron released from P700 is transferred to a terminal acceptor atthe reducing end of PSI through intermediate acceptors, and the electronis transported across the thylakoid membrane.

Natural photosynthetic systems have been modified to contain colloidalmetallic platinum at the reducing site of PSI in thylakoid membranes inorder to make metallic catalyst systems (see, for example, Greenbaum,1985; Greenbaum, 1988; Greenbaum, 1990; Lee et al., 1990; Lee et al.,1994). In these reactions, molecular hydrogen is synthesized throughreduction of protons by a reaction that is catalyzed by the platinumcolloidal particles adjacent to the reducing site of PSI on the stromalside of the thylakoid membrane. Platinization of PSI can be accomplishedthrough either chemical precipitation (such as platinum precipitation byH₂ purging) or preferably by in-situ photochemical reduction of platinumchemical precursors into metallic platinum colloid. Both chemical andin-situ photogenic reductive precipitation of metal platinum occur inclose proximity to the PSI reducing end, indicating that metalprecursors (e.g., [Pt(Cl)₆]²⁻) have high affinity for the PSI reducingend (Greenbaum 1988; Lee et al., 1994). It has been shown that theplatinization process does not impede the intrinsic photosyntheticactivity, e.g., electron transport (Greenbaum, 1990; Lee et al., 1995),and that the properties of PSI reaction centers are stable underrelatively long-term storage (Lee et al., 1995). Importantly, becausehydrogen is synthesized during the photoreductive precipitationreactions described herein, hydrogen evolution can be used as asensitive indicator of metal particle formation on PSI (Greenbaum,1988).

A film, as the term is used herein, refers to a film or coating at leastpartly comprised of and/or made from the nanoparticles described herein.Typically, the film will be supported by a solid substrate, such asthose comprised of metal or ceramic, e.g., gold, silicon, silica,titania, zirconia, and the like. For most applications, the films willhave a thickness in the range of about 1 nm to 5000 nm. Because of thehigh degree of control offered by this invention, high quality films inthe range of about 1 nm to 100 nm are preferably produced. The metallicfilms produced according to the invention may be formed as composites oralloys with other materials. Additionally, they may contain residualproteinaceous material as a result of the presence of PSI-containingunits present during some film forming processes

In one embodiment of the present invention, a method is provided forproducing films from metallic nanoparticles using liquid suspensionscomprised of photosystem I-containing units, metal precursor compoundsand electron donor compounds. Additional components may also be presentin the liquid suspension, for example, organic monomers, depending onthe requirements and/or preferences of a given application. The liquidsuspension is contacted with light under conditions in which the metalprecursor undergoes reductive precipitation at the reducing end of thePSI particle of the PSI-containing unit. As a result, metallic particlesare provided in the form of photosystem I-metal complexes in the liquidsuspension. The size of the metallic particles in the PSI-metalcomplexes is directly related to amount and intensity of light energyadministered. Consequently, particles having desired dimensions may becontrollably synthesized.

The PSI-metal complexes are provided above a solid substrate, typicallyby applying a volume of the suspension on the surface of the substrate.The substrate may be one upon which the liquid suspension was previouslyapplied prior to formation of the PSI-metal complexes. Alternatively,the PSI-metal complexes may be formed in a separate liquid suspensionvessel and the liquid suspension may be thereafter applied above thesubstrate surface. In one preferred approach, sol/gel techniques areused wherein the substrate is dipped directly into the liquid suspensioncontaining the PSI-metal complexes or the liquid suspension containingthe PSI-metal complexes is spin coated onto the substrate. Such methodsmay be preferred where a high degree of thickness control is desired.Substantially all of the liquid present in the liquid suspension isremoved from the coated substrate, for example by air drying or byapplying heat, vacuum, etc., to cause evaporation of the liquid. Thisprovides on the surface of the substrate a film comprised primarily ofPSI-metal complexes.

Films having a variety of structural features may be obtained by thisapproach. For example, microporous films may be produced by coating thesubstrate with a liquid suspension comprised of a mixture of PSI-metalcomplexes wherein the PSI-containing units are thylakoids.Alternatively, nanoporous films may be provided by using liquidsuspension containing PSI-metal complexes wherein the PSI-containingunits are isolated PSI particles. Thus, the size of the biologicalcomponents present in the PSI-metal complexes will determine to someextent the size of the pores in the materials following removal of thebiological components from the films, e.g., by sintering. In addition,dense nanophase films can be provided by coating on the substrate asolution containing substantially pure metallic nanoparticles which havebeen separated from the PSI-metal complexes.

According to another embodiment of the invention, metallic filmfabrication can be achieved on an ordered layer of PSI-containing unitsanchored or otherwise coated on the surface of a substrate (such asgold, silicon, alumina, etc.). These PSI-coated substrates have beendescribed (see, for example, Rutherford and Sétif, 1990; Lee et al.,1996; and Lee et al., 1995). The types of interactions (e.g., covalent,electrostatic, etc.) between the PSI-containing units and the substrateare not critical provided they are substantially stable in the liquidsuspensions in which the photoreactions will be performed and they donot preclude the availability of the reducing end of the PSI unit forreductive metal precipitation.

The PSI-coated substrate is contacted with a solution (or,alternatively, could be exposed to vapor) that contains the desiredmetal precursor compounds and electron donor molecules. Light exposureof the PSI-containing units on the substrate leads to the reductiveprecipitation of the metal, as described above. However, in thisembodiment, metal particle formation is spatially constrained along thesurface of the substrate where the PSI-containing units are anchored. Bycontrolling the input of light energy and the number of light pulses,and therefore particle growth, a biomolecular “welding” effect may beachieved on the PSI-coated layer, in which adjacent metallic particlesprecipitated on the PSI-containing units grow sufficiently large andeventually coalesce into a continuous metal film. The size of metalparticles and the thickness of the film that is formed can therefore beprecisely controlled by exposing an appropriate amount of light energyon the photoreactor system. Of course, the light input required to forma film having a desired thickness will depend to some extent on thedensity of the PSI-containing units coated on the substrate prior tolight-induced metal precipitation.

Although thick films may be produced according to these methods, thinfilms having nanometer range thicknesses, e.g., 1 to 10 nm, arepreferably synthesized to take advantage of the precise depositioncontrol offered by this invention. None of the traditional film-formingtechnology, such as CVD, PVD, sputtering, or epitaxial growth canprovide a comparable level of control. Moreover, the films of thisinvention can be advantageously provided as patterned metal layers usingconventional photolithographic techniques.

In another embodiment of the invention, a method is provided for theproduction of metallic nanoparticles. In this approach, desiredPSI-metal complexes are formed as described in the above embodiments.However, the PSI-metal complexes are not applied to a substrate toeffect film formation. Rather, after the light induced reductiveprecipitation reactions, the PSI-metal complexes are treated in a mannerwhich allows for the separation of metallic particles from thePSI-containing units. This can be accoplished by any of a number ofapproaches. For example, the PSI-metal complexes could be treated withvarious surfactants, e.g., sodium dodecyl sulfate (SDS), or could besubjected to sufficent agitation, ultrasonication, etc., in order todisrupt the association between the metal particles and the PSI-units.Alternatively, the biological components present in the PSI-metalcomplexes could be solubilized with an organic solvent or degraded usingenzymatic reactions, e.g., using nucleases, proteases, etc, to removethe metal particles provided the treatment does not unacceptablycompromise the integrity of the particles. Upon dissociation of themetal particles from the PSI-units using an approach such as thosedescribed above, the metal particles can be readily separated by one ormore density-based separation techniques.

The metal precursor compounds used in conjunction with this inventioncan include any of a variety of compounds capable of undergoingreductive precipitation to form a desired metallic species. The metalprecursors will typically comprise ionic metal salts capable ofaccepting electrons from PSI such that upon transfer of one or moreelectrons, the metal precursors are reduced to a pure metal form.Suitable metal precursors for producing the metallic particles of theinvention may include, without limitation, ionic salts of platinum,palladium, osmium, ruthenium, iridium, silver, copper, indium, nickel,iron and tin, such as chloride-derived, sulfate-derived andnitrate-derived salts of these and related metals. Particularlypreferred metal precusors for use in the invention includehexachloroplatinate ([PtCl₆]²⁻), hexachloroosmiate ([OsCl₆]²⁻), andhexachloropalladinate ([PdCl₆]²⁻).

The electron donor molecules which are included in the liquidsuspensions according to the invention should of course be compatiblewith the PSI electron pumping system that is employed. The electrondonor in most applications will be water, however some organic moleculesmay be present in the liquid suspensions which serve as facilitators ofthe electron transport process. These may include, for example, EDTA,proflavin, methylviologen, and the like. The concentration of thesefacilitator molecules, when present, will typically be in the range ofabout 10 mM to 100 mM in the liquid suspension.

Essentially any light source may be used in accordance with theinvention provided it can generate light in a visible portion of thesolar emission spectrum. Typically, the wavelengths of light mosteffective for causing PSI electron pumping activity will be betweenabout 400 and 700 nm. Although the light exposure of the PSI-containingunits may be continuous, it will generally be preferred to useintermittent pulses/flashes of light given the level of control thisprovides over particle growth. Intermittent illumination with a pulsedflash light source (e.g., a stroboscopic flash lamp) can providequantitative control of the deposition at the reducing sites of PSI, onemetallic atom at a time. Numerous such light sources are available, suchas the GenRad Model 1539A xenon flash lamp. Preferably, the flash lampsare coupled with a trigger generator, such as the Hewlett Packard Model8011A. This device allows the frequency of the trigger pulses to bevaried from 1 to 400 Hz, the range of frequencies over which the xenonflash lamps may be fired without degrading light output.

In addition to the nanoparticles and continuous thin films describedabove, metallic patterns of nanoscale resolution may be prepared on asubstrate surface by coupling laser and/or electron beam lithographytechniques with the methods of this invention. For example, aposition-controllable laser beam could be used to provide precisedeposition of metal particles and/or lines in essentially any desiredpattern on the surface of a PSI-coated substrate.

If the substrate on which the deposition is performed is a ceramic, theinvention can be readily adapted for the fabrication of various types ofmetal-ceramic membranes, e.g., (1) dense or porous metallic membranesthat are supported on porous ceramic membranes; (2) metals depositedinside the pores of ceramic membranes; and (3) metals coated on solidparticles that are partially sintered onto inorganic membranes.

The following example is provided to illustrate one embodiment of thisinvention. The techniques disclosed in the example which followsrepresent those projected by the inventors to function in the practiceof the invention and thus can be considered to constitute an example ofone mode for its practice. However, those skilled in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments which are disclosed and still obtain alike or similar result without departing from the spirit and scope ofthe invention.

EXAMPLES Photobiomolecular Deposition of a Platinum Film

Type C chloroplasts are isolated according to the method of Reeves andHall (1980). In this preparation, the chloroplast envelope isosmotically ruptured, exposing the thylakoid membranes to the externalaqueous medium. The thylakoids are suspended in Walkers assay medium andadjusted to a final chlorophyll concentration of about 3 mg. A solutionof chloroplatinic acid neutralized to pH 7 is added in the dark to thethylakoid suspension to give a final concentration of 1 mM in thesuspension (this value is not critical provided there is an excess ofhexachloroplatinate ions to photosystem I reaction centers). The liquidsuspension is illuminated with a xenon stroboscopic light source (GenRadType 1539) set to be triggered by a pulse generator (Hewlett-Packard8011A). The frequency of the flashing is 10 Hz and the duration is 3μsec at half height. Pulsed light exposure of the suspension isperformed for 90 minutes. Following the light treatment of thesuspension to form the desired PSI-metal complexes, the suspension isspin coated on a silicon substrate at about 25° C. to provide thedesired film. The PSI-film so produced will exhibit photocatalyticproperties and vectorial electron transport, and will be useful, forexample, as a photocatalyst.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. More specifically, it will be apparent that certaincompounds that are chemically, structurally and/or functionally relatedto those disclosed herein may be substituted in the methods of thisinvention while the same or similar results would be achieved.Furthermore, no limitations are intended to the details of constructionor design herein shown, other than as described in the claims below. Itis therefore evident that the particular embodiments disclosed above maybe altered or modified and all such variations are considered within thescope and spirit of the invention. Accordingly, the protection soughtherein is as set forth in the claims below.

REFERENCES

Boardman, Methods Enzymol, 23:268, 1971.

Greenbaum, “Platinized chloroplasts: a novel photocatalytic material,”Science, 230(4732):1373, 1985.

Greenbaum, “Interfacial photoreactions at the photosynthetic membraneinterface: an upper limit for the number of platinum atoms required toform a hydrogen-evolving platinum metal catalyst,” J. Phys. Chem.,92:4571, 1988.

Greenbaum, “Biomolecular electronics: observation of orientedphotocurrents by entrapped platinized chloroplasts,” Bioelectrochemistryand Bioenergetics, 21:171, 1989.

Greenbaum, “Vectorial photocurrents and photoconductivity in metalizedchloroplasts,” J. Phys. Chem., 94:6151, 1990.

Greenbaum, “Kinetic studies of interfacial photocurrents in platinizedchloroplasts,” J. Phys. Chem., 96:514, 1992.

Lee, Tevault, Blankinship, Collins, Greenbaum, “Photosynthetic watersplitting: in-situ photoprecipitation of metallocatalysts forphotoevolution of hydrogen and oxygen,” Energy & Fuels, 8:770, 1994.

Lee, Lee, Warmack, Allison, Greenbaum, “Molecular electronics of asingle photosystems I reaction center: studies with scanning tunnelingmicroscopy and spectroscopy,” Proc. Natl. Acad. Sci. USA, 92:1965, 1995.

Lee and Greenbaum, “Bioelectronics and biometallocatalysis forproduction of fuels and chemicals by photosynthetic water splitting,”Appl. Biochem. Biotechnol., 51(52):295, 1995.

Lee, Lee, Greenbaum, “Platinization: a novel technique to anchorphotosystem I reaction centers on a metal surface at biologicaltemperature and pH,” Biosensors & Bioelectronics,, 11(4):375, 1996.

Reeves, S. G.; Hall, D. O., Methods Enzymol. 69: 85-94, 1980.

Rutherford and Setif, “Orientation of P700, the primary electron donorof photosystem I,” Biochimica et Biophysica Acta, 1019:128, 1990.

Sétif, Acker, Lagoutte, Duranton, Photosynth. Res., 1:17, 1980.

What is claimed:
 1. A metal nanoparticulate deposit produced by thesteps of: preparing a sample comprising an electron donor,protein-chlorophyll photosystem I (PSI) units and a metal precursorreducible by said PSI units, said PSI units disposed in an ordered arrayon a substrate; inducing single or multiple electron emission from thePSI units under conditions that reduce one or more atoms of the metalprecursor to form a plurality of PSI/metal complexes, said complexeseach including a PSI-containing unit bound to a metal nanoparticle;wherein said plurality of complexes form an ordered array on saidsubstrate, each of said metal nanoparticles ordered around said PSIunits.
 2. The metal nanoparticulate deposit of claim 1 wherein the PSIunits of the complex are removed to provide a polycrystalline nanoporousfilm, said polycrystalline nanoporous film comprising a plurality ofmetal nanoparticles.
 3. The metal nanoparticulate deposit of claim 1wherein said metal nanoparticles have sizes from about 1 nm to about 100nm in diameter.
 4. The metal nanoparticulate deposit of claim 1 whereinsaid metal nanoparticles have sizes from about 1 nm to about 10 nm indiameter.
 5. The metal nanopartioulate deposit of claim 1 wherein saidnanapartioles comprise a plurality of metal atoms, said nanoparticlesbeing within a predetermined size range, said size range varying by nomore than a size of said metal atoms.
 6. The metal nanoparticulatedeposit of claim 1 wherein said ordered array of complexes form ananoporous film, said nanoporous film having a thickness of from about 1nm to about 100 nm thick.
 7. The metal nanoparticulate deposit of claim1 wherein the substrate is at least one selected from the groupconsisting of gold, silica, alumina, zirconia, titania, silicon, glassand plastic.
 8. The metal nanoparticulate deposit of claim 7 wherein thesubstrate is silicon.
 9. The metal nanoparticulate deposit of claim 1wherein the metal is at least one selected from the group consisting ofplatinum, osmium and palladium.
 10. The metal nanoparticulate deposit ofclaim 1 wherein the metal is platinum.
 11. A metal containing assemblydisposed an a substrate, comprising: a plurality of metal nanoparticles,said nanoparticles comprising a plurality of metal atoms, saidnanoparticles being within a predetermined size range, said size rangevarying by no more than a size of said metal atoms.
 12. The assembly ofclaim 11, wherein said metal nanoparticles are disposed in an orderedarray on said substrate, each of said metal nanoparticles ordered arounda point of origin.